Yarn curling apparatus



Sept. 5, 1961 P. VAN DIJK YARN CURLING APPARATUS Filed March 9, 1959INVENTOR. PIETER VAN DIJK BY ATTORNEY United States ew This inventionrelates to the heating of synthetic thermoplastic threads or yarns andmore particularly to an apparatus for heating such threads or yarns whenused 'in conjunction with a yarn curling apparatus including a twistingdevice.

In U.S. Patent No. 2,869,312, having common ownership herewith, a yarnheating apparatus is described. This yarn heating apparatus may be usedin conjunction with a yarn curling apparatus which includes a twistingdevice. Therein is described, as one embodiment, a yarn heatingapparatus comprising an electrically heated, elongated tube having alongitudinal opening presenting a smooth inner surface. The diameter ofthis opening is not substantially greater than the diameter of the yarnto be curled. The yarn is passed through this opening in contact withsubstantially all portions of this inner surface and at the same time istwisted and vibrated by the twisting device. The heating tube is made ofa material suitable for heating by electricity and has very thin walls.

There are certain disadvantages to the use of such thinwalled heatingtubes. It has been found that the thinwalled tubes very often do nothave a homogeneous resistance thereby preventing even distribution ofheat over the length of the tube. Also, such tubes have a tendency to bedeformed on heating, thereby necessitating mount.- ing under strainwhich unduly complicates the apparatus.

A further disadvantage occurs upon the discontinuance of movement ofthread through the tube. The thread remaining within the tube Withdrawsless heat than during normal operation. As a result, the temperature ofthe tube increases and may melt the thread.

Therefore it is an object of this invention to provide a heating tubenot having disadvantages of known heating tubes and which is suitablefor use in conjunction with a twisting device.

It is a further object of this invention to provide a heating tube thathas an even distribution of heat over its inner surface.

An additional object of this invention is to provide a heating tube thatdoes not require mounting under strain.

It is a further object of this invention to provide a heating tube thatdoes not increase in temperature upon stoppage of thread movement tosuch a degree that the thread melts.

These and other objects of this invention will become apparent from areading of the following detailed specification, in conjunction with theaccompanying drawing wherein the figure is a diagrammatic view, inelevation, illustrating a continuous curling apparatus including theimproved heater of this invention.

It has been found that these objects may be obtained and thedisadvantages of the previously described heating tube may be overcomeby utilizing a heating tube whose external diameter exceeds 2 mm., andordinarily will not exceed 5 mm.

Such a tube, when constructed of material having suitable electricalresistance, makes possible a more uniform distribution of heatthroughout the entire length of the inner surface of the tube. The tubemay be constructed of any suitable resistance material, however, thepreferred material is stainless steel.

It is contemplated that this tube will be used in conjunction with athermoplastic thread or yarn curling ap- 2 395,593. Patented Sept. 5,1961 paratus which includes a twisting device. The advantages of such atubeare not obtainedjexcept in conjunction with such anjapparatus;This'heating tube will have an inner diameterof' less 0.8. and anexternal di-. ameter of .more than 2 Stated differently, the tube 7 wallthickness, whichis. one half the difference between external andinternal diameters, should be at least 0.6 mm. and preferablyshould-begreater than in excess of the internal tube diameter.

Referring now to the drawing in which thermoplastic A yarn 10 having,for purposes of illustration, a denier of 70 is withdrawn from supplypackage 11 through thread guide 12, tension device 13, and thread guide14. From thread guide 14, the yarn passes into heater 18. Tension device13 is a conventional tension device. Heater 18 is constructed ofstainless steel and has an internal diameter of 0.5 mm. and an externaldiameter of 2.5 mm. It can be seen from arithmetical calculations,therefore, that the tube wall thickness, derived in the manner describedabove, is twice the internal tube diameter, or in excess of the internaltube diameter. Heater 18 is an elongated hollow body or tube and issupported by arms 19 and 20 from a block of insulating material 21 whichcan be supported from a convenient part of the machine by means notshown. Electrical conduits 22 and 23 provide for an electric heatingcurrent to be applied to tube 18. The current is led to the tube fromconduits 22 and 23 through arms 19 and 20.

The inner surface of tube 18 is smooth and polished. The size of theaperture in the tube is so nearly the diameter of the yarn 10 thatsmall, low amplitude oscillations of the yarn will cause it to contactthe inner wall of the tube 18 in very nearly all of its radii.Similarly, nearly all of the surface of each length of yarn is caused tocontact some portion of the heating surface and the result is aconsiderable conservation of heat and improvement in the uniformity ofheat application to the yarn being treated.

From heater 18, the yarn passes into and through a false twisting device24 which is rotated by belt 25 and drive motor 26. The device 24 impartsa false twist to yarn 10, which twist subsequently is removed prior totake-up. The false twisted yarn passes through a cooling zone 27 andonto withdrawal godet 28, at which point substantially all of the twistis removed. Yarn leaving godet 28 is passed over guide roller 29 andcollected on yarn take-up means 30. i

The temporary twist imparted to yarn 10 by false twisting device 24travels longitudinally of the yarn to such an extent that curled yarn iscontained within heater 18. Device 24 causes low amplitude oscillationsof yarn 10 which oscillations travel longitudinally of the'yarn to suchan extent that the yarn in heater 18 oscillates and contacts nearly allof the inner surface of heater 18 at some time.

The curls in the yarn 10 are set by heater 18 and remain to a largeextent after removal of the false twist. If desired, thermostat 31 maybe provided for controlling the amount of heat to which the yarn issubjected.

For additional details of this false twisting apparatus and controlmeans for supplying yarn to heater 18, reference should be had to U.S.application Serial No. 513,442, filed June 6, 1955, now Patent No.2,949,721, and having common ownership herewith.

Inasmuch as other embodiments will become apparent to those skilled inthe art, it is intended that the scope of the present invention belimited only to the extent set ,j" 3 resistance element having alongitudinal opening presenting a smooth inner surface through whichsaid curled yarn is passed, the diameter of said opening being notsubstantially greater than the diameter of the yarn to be curled and thethickness of said elongated body between the longitudinal opening andthe external surface thereof being in excess of said diameter by atleast 75%, electrical means connected to said body for heating the sameand thereby setting the curl imparted to said yarn by said twistingdevice, and means for passing thermoplastic yarn longitudinallythroughsaid opening in contact with substantially all portions of saidinner surface while imparting twist and vibration thereto with saidtwisting device.

References Cited in the file of this patent UNITED STATES PATENTS

